A Michigan natural gas utility was upgrading a gate station that had been in service since the early 1980s. The existing odorization infrastructure included a 2,500-gallon underground bulk odorant storage tank, 26 inches in diameter and 90 feet long, along with a 165-gallon vertical day tank, an associated flare, an odorant pump, and roughly 1,000 feet of odorant-contaminated piping running both above and below grade.
The underground tank had been buried for four decades. Its interior surfaces carried decades of absorbed mercaptan that would continue to off-gas for years if the tank were moved without proper treatment. Standard practice would be to remove the tank to MRR’s processing facility in West Virginia for off-site treatment — but at 90 feet long, the tank was beyond what could be transported in one piece. The project required a different approach.
Approach
MRR designed a fully on-site treatment operation. The work sequence had to accomplish several objectives simultaneously: relocate the residual odorant from the existing system to an alternate utility station so it could continue in productive use, isolate and remove the contaminated piping network without releasing odorant into the surrounding environment, excavate and de-odorize the 90-foot tank in place, and prepare the site for the operator’s new equipment installation.
The residual odorant — approximately 215 gallons — was filtered and transferred from the existing tank to an MRR bobtail truck for relocation to a designated utility station. The 1,000 feet of contaminated piping, both above and below grade, was identified, isolated, and removed in segments. The flare and odorant pump were decommissioned and removed in parallel.
The 90-foot tank itself was excavated to expose the full length, then treated on site using MRR's on-site de-odorization process. The process reduced absorbed mercaptan in the tank interior to a level below detection thresholds, allowing the tank to be cut into transportable sections for removal to recycling. No portion of the tank left the site carrying the absorbed odorant reservoir that would have caused community odor complaints during transport.
Outcome
The full project — odorant relocation, piping removal, tank excavation, on-site treatment, cutting, and final removal — was completed in two weeks. The 215 gallons of residual odorant continued in productive use at the alternate station. The treated steel from the tank entered the standard recycling stream. The site was returned to the operator clean and ready for new equipment installation.
The operator received a complete documentation package covering the regulatory notifications, the chain of custody for all removed material, the on-site treatment record, and the final disposition certifications for both the treated steel and the contaminated piping. The closure file is what the operator’s compliance team will reference for any future audit, acquisition due diligence, or environmental review of the site.
Most decommissioned equipment leaves MRR customer sites under hazmat manifest, bound for treatment at the Philippi plant in West Virginia. The Michigan tank stayed in Michigan because it had to. On-site treatment is the path when transport is not.
